Party-line automatic telephone system.



E. A. MELLINGEII. PARTY LINE AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED IULY 9,1907.

3 SHEET *SHEET Ix iIII.

I. x. I I ...ml f

Patente Mar. 21,1l.

Q l Now.

4. ZAM

t` A. MELHNGER.

mm UNE ANUMAN@ FELEPHQNE SYSTEM.

APPLICATION F|LED1Ul.Y,190.

Patented 'Mz-11'. 21, 1916.

3 SHEETS-SHEET 2` @E TED STATE@ iiiii OFFCE.

EDWARD A. MELLINGER, OF CHICAGO, LLINQS, ASSGNGB, BY 'MESNE ASSIGNMENTS, TO FIRST TRUST A273 SAVINGS BANK, TR'US'EE, OF CHICAGO, ILLINOIS.

PARTY-LINE AUTOMATIC TELEPHONE SYSTEM.

Application 'ied July 9, 1907.

relates totelephone systems in 1j more particularly to automatie te v exchange. systems, and ciali? .us in which plurality or iimis are loeatefl on the saine ai', s f, tems in which party 1mi.

eets my present invention is in the nature or an improvement on party` line syste: .in which a. relay is provided for niomeniarny removing' the guarding putential from the ceiling line, to permit a suhscriber thereon to call another subs rihcr on the same iine. This relay controls-a circuit through the hridgecut-oi relay of the eaiiing line. For this reason prior to my present invention it was found that in releasing', the [aid cut-oli' relay was liable to he Lio miergixed, with the result that the trip mag; net oi the int" iual siriteh of line u'o'uhi. he energizeri. ilis vias found to re-V sult in leaving the individual switch olif-normal, which, of course, would occasion some trouble.

The principai object of my prese. t invention is, therefore, to provide an improved system oi" the foregoing character in which the switches can oe rele-asini without any liability of energizing the trip magnet or the partyine, and whereby there will loe no (tanger of the individual trunking; suf'iteh being i "t it nornial after the subscribers ainl connector E, hack tothe saine line Specification of Letters Eatent.

Patented Mar. 21, 1916.

ieai No. $212,914. r

to the three substations Fig. 2 represents, y, hut more fully, the al tie controlling master 5 a etait-view of the bank Figs. 4, 5, G, 7, 8, 9

showing the said springs in `stations may be of any suitable or il type. Those in connection with :we elected to illustrate my inven- Suhstation A, for example, a receiver a switch-hook 3 for 1' station circuits, which 'ions 'are accomplished 4in oi"- any suitable means, i A raixrarnis 4, 5 and G, As the lowered the canrarm 4 mowes/ses the release springs 7, 8 rement, whereby the substamay he grounded simultlie switch-hook is down igres the spring 10, thereijer 11 in series with the s the. line. Furthermore, tfrhool: down the said cam- ,iges the springs i3, 14 and 15, ne' the local battery circuit which l the prin'iary winding 15, c' iu au-il local battery l. When s i3 and M fiisengage, the lock M* is fiiseennected from the vertiniuetor. 'The substation ground s normally broken between the i8 and lil by the eam-arm;

the spi 'out ie rai lin(Y circuit ground spring but xvii und sp rugs are together, and the a dial inot shown) which is secured to the Ihaft togetner with the locking dog. Furthermore, there 1s a locking cam 27 that dog 26 while the receiver is on the locks ti sxritcirhook, to prevent a rotation of the dial. .F or operating the impulse Isprings 23 and 24 the substation is `provided with an impulse wheel 28 that is 'secured to the shaft, which impulse Wheel carries on its peail views of the substation immember 253. As the impulse 4) on the under side,.with which riphery the so-called vertical impulse teeth 29 and one rotary impulse tooth 30. The said impulse teeth are' so arranged that when thc dial is drawn down the impulse spring 23 is not carried into contact with the ground post 20; but as the dial returns, first the vertical teeth engage the vertical impulse spring 23, and after they have completed their work the rotary impulsetooth `30 operates the rotary impulse spring 24. ln this operation thesubscribers vertical line conductor 31 is first given a number of ground impulses, and then the rotary line conductor 32 is given one ground impulse. The vertical impulse spring 23 is provided with an oblique projection or lug-250 (Fig. the vertical lmpulse teeth 29 are adapted to engage for driving the spring 23 intermittently onto the ground post 20. The rotart spring 24 is provided with somewhat similar mechanism for driving th said rotary spring onto the ground pos/t, once whenthe dial is rotated 'in one direction, and once when rotated in the opposite direction. The said rotary impulse spring 24 has on its under side a V-shaped sides c and d. In addition, there is an auxiliary spring 252 which works in conjunction with the said V-shaped member. vAs shown more clearly in Fig. 4, the auxiliary spring 252 is provided with a lower curved part 253 having the rear section 254 curving outwardly, as shown also in Figs. 5, 6, 7, 8, 9 and 10. The front section 255 of said member 253 is designed to fall just below the apex of the V-shaped member 251, so that the rotary impulse tooth 30, when moving in the direction indicated by the arrow 'in Fig. 5, will pass onto the curved member 253, thus pressing the rotary impulse spring 24 onto the ground post 20,for a compara-d tively long time, as shown in Fig. 6, thus sending to the rotary line a comparatively long impulse As the impulse wheel advances, the vertical impulse teeth 29 ap- -preach the iug` 250 of the vertical impulse spring 23 (Fig. 6), and eventually the first tooth f meets the lug 250 clears the said lug, as shownn Fig. 7, but not until after the rotary impulse tooth 30 clears the curved wheel continues to advance in the direction indicated by the arrow in Fig. 7, the succeeding imH pulseA tooth will 'clear the projection 250, as shown in Fig. 8. Then when the impulse wheel is released, first the vertical impulse spring 23 is carried into engagement with the ground post 20 twice by the vertical impulse teeth previously cleared, as indicated in Fig. 9; but as the impulse wheel nears its normal position the rotary impulse tooth 3.0 passes under the curved member 253 of the auxiliary spring 252 (Fig. 10) engaging the Avl-shaped member 251 for a short time only,

v impulse switch-hook 3 is moving member 251 having two sending the ordinary impulse .to the rotary llne through the medium of the rotary impulse sprlng 24; after which the said member 251 is cleared, as shown in Fig. 5, as the engages the contact point 38, whereby the vertical line conductor 31. may be grounded.

The substation is also provided with a governor (not shown) for controlling the speed of' the impulse wheel 28 and the switch-hook 3. Furthermore, the lock-out relay 17a is provided with the armature 39, so that when the relay a up,'the armature 39 1s attracted, disengaging the springs 40 and 41, and the armature is locked in its attracted 'position by the locking spring 42, as yshown at substation #220; but when the switch-hook is lowered the rod 43, which is attached to the switch-hook 3, slides downward in front of the armature 39, car- 'rying the locking spring 42 out of en agcment with the armature 39. The individual or line switch "C (Fig. 2) is of the general form disclosed in British Patent N o. 26301 of 199,6. The said switch comprises a plungar 44, plunger-arm 45, bridge-cut-ofi relay 46, trip magnet 47 and switch-release magnet 48, all of which are built about a switchbase or frame (not shown).. The saidA switch-release magnet is provided vwith an armature 1.49 that is pivoted on a pin 50 which ,rises from the base of the switch. The said armature carries pivotally secured the armature 51 is'secured the catch spring v 56 which is adapted to engage the end 57 of the plunger-arm 45. Furthermore, the said line switch is provided with a bank of terminals, usually ten in number but only one of which is shown at Q in Fig. 2. As shown, the said terminal Q is turned from its true position with respect to the swing of the plunger 44, and the bushing 62 is correis energized as the Vionits end a second armature 51 that is con i spondingly turned, all for the purpose of making the illustration clearer. The termim nal Q comprises the springs (33 and 64, (S5 and 6G, 67 and 68, and 69 and 70. The said springs are normally disconneeted from each other, but are driven into contactiu the above-mentioned order when the plunger 44 operates. lVhen the plui'iger 44 is in locked engagement with the plunger shaft 60, the notch 61 is in engagement with the ange or web of the shaft 60. and when in sliding engagement the end 59 rests iu the position shown by the dotted lines in Fig. Zh-that is. when the plunger shaft is operated the plunger 44 is not carried along with the locked plungers, but remains in the dotted position. the plungershaft sliding upon the. end 459, Normally, however` the plunger 44 is' 'retained out of engagement with the line switch bank, and in engagement with the plunger-controlling shaft (Slt which latter is operated by the master switch H. T he general operation of the switch is as fol lows: The trip magnet 47 is energized by a preliminary impulse, and the armature .il is attracted against the magnet cores. Villien the armature 51 is attached the catch 5H slides out of Contact with the end 57 of the plunger-arm 45. and the said plungerairm 45, owing to the tension of the spring 58, moves about the pin 54 and thrusts the plunger 44 into the bank terminal Q. shown in Fig. 2; and when the trip magnet again deenergizes, the trip armature 51 falls against the end of the plunger-arm 45. The switch is restored when the release magnet 48 be.' comes energized, whereby th` armature 49 attracted, and accordingly1 the trip armature 51 is moved upwardly until the catch 56 slides over the end 57; then when the release magnet 48 becomes deinergized the armature 49 returns to normal position and remains at rest against the stop 55. Furthermore, since the plunger-arm 45 is now in engagement with the armature 51. the said plunger-arm is also moved about the pin 54, whereby the plunger 44 is moved from the terminal Q. Also, since the pluuger shaft has advanced one step. the hub 59 of the plunger 44 cornes to rest in the posiv tion shown by the dotted lines` in `Fig. 2. l.ugainst the plunger shaft 60, and as the said plunger shaft advances each time an idle trunk is seized, the plunger 44. is not advanced., but remains iu this position and opposite the trunk terminal from which it has just disengaged7 since the slot 61 is not in engagement with the plunger shaft (30. After all the trunk lines have been ,successively seized, and the shaft G0 is released from its last position, said shaft then starts toward home or starting point and picks up the plunger 44, when the flange 0r web of the said Shaft, over, which the slot G1 normally rides, arrlves at the position from which the plunger 44 was originally released. From thence on the plunger44 is carried by the shaft G() until it is again released when another call is made. But if after the plunger is released, and before the shaft GO returns to piek up said plunger, the switch C is again operated, the plunger 44 again engages the same terminal Q.

The master switch H, which may be of any suitable or approved type, is provided for operating the plunger shaft G0, and for controlling certain circuitsl that will be disA closed hereinafter. lt conpVisi-s` the following details: a motor magnet il for operating the ratchet wheel TL. which latter is designed for operating the plunger shaft GO through the medium of the cani-arm Til. and a differential relay TP for controlling the energizing 'circuit oi the motor magnet Ti. The said master switch also has a bank (i) comprising a pluralit)r of individual contact segments a. and a common metallic nient T4. as shown in Figs f and il. The indi.'if.lual segments :if are separated from the common segment 'il (Fig. il) by the insnlating strip TQ, The insulin g member Tll is provided so that when the wipeil 75' Vmsses ironi the extreme left coutaet lll4 to the extreme right contact *34. the upper part 75 slides on the piece 'p'k thuspreventing the wiper arm T5 from placing the contant segments u. in cfmneetion with the common segment 74, whereby seine interference n'iight be experienced by the master switch. The wiper 75 is adapted to remain in con stant engagement, with the bank (Y). and to maintain at all times some one of the seg ments (i in ele-iftvical ."oniectn'eu w th the con'inidn sei ynent i4, except when thowiper i'i passes from the extreme left contact 164 lo the cxtreme right contact Ii4. as explained. The wiper T3 is oi'ierated in a -itcp-lrvHstci manner bv the ratchet wheel T72, through the, medium of a Cain member 'lo ri idly secured to the .said wiper 'To and adapted to sucees sively engage the pins T7, 75l, T9 and 80 upon the `said ratchet wheel T2. The motor magnet 7l is provided willi an armature l. upon the end oi" which vthere, suitably aeeured a pawl @il lhxch time that thc said. magnet is energized the pawl Si engages the ratchet wheel T2. advaneing the latter one step, lt will be seen. therefore. that as the ratchet wheel 72 advances. the wiper 75 also advances` .stepdiv-step from iight io lett.r` and when the pin 7T, for instance. clears the cam 7S the retracting spring 552i nfstores the wiper T5 to its first position at the right oit the bank (l and in engagement with the lirst segment 84. rihe said motor magnet Tl is provided with a couple of interruptor springs and 8G that are included in the energizing Circuit of the said motor inagnet, which energizing circuit also compri *is the springs 8T and mutrolied by the diiill) (jfl

ferert al relay 73. Therefore, whenever the differential relay 73 is energized the springs 87 and 88 lare pressed into Contact, and the motor magn'et 71 operates step-by-step as long as the differential relay 73 remains energized. Further, it is assumed that the terminal Q of the line switch C is he first terminal of the line switch' bank. The plunger 44, while in normal locking ment with the shaft 60, is retained in front of said terminal by the plunger shaft G0, whenever the master switch wiper 75 is in engagement with the bank segment S4; but as the motor magnet 71 advances the Wiper 75 onto the second segment 89, the said plunger and all idle plungers similarly engaging the shaft are carried opposite the next terminal of the line switch bank.

lt'should be notedA that in each switch bank all of the springs 63 are permanently connected and may be made of one common piece; the springs 61, however, are individual-that is, there is...one separate and distinct spring for every terminal Q, there being ten in the bank. The springs G5, 67 and 69, like the springs 03, are also com mon, and the springs G6, 68 and 70, like the springs 64, are individual.y For every bank terminal Q there is a trunk line o three conductors 90, 91 and 92 leading to a selector; and there is also a normal trunk line comprising the conductors 93, 94 and 95 leading to the connector banks. The subscriber`s line conductors 31 and 32 terminate in the springs 63 and 65 which, as has been stated, are common springs. iVhen the subscriber operates the line switch C, and the plunger 44 engages the terminal Q, the subseribers line conductors 81 and 32 are ex tended to the vertical and rotary conductors 90 and 91, thence to the switch D.

As shown in Fig. 1, the private normal relays 113 and 114l are bridged across the trunk line conductors 90 and 91. The arrangement of these relays is such that when impulses are passing over the vertical line conductor the vertical private normal relay 113 energizes and operates to place `the spring 123 in contact with the ground spring' 124; and the rotary private normal relay 114 operates to disengae.' the Y:rings 116 and 117 when. the retail' impl e rotary line con utter. 'i'i arrangement is providmi in eine. that a subscriber may call back upon his own l' l yhat is, when a ros tary .impulse is delivered the relay 114 en ergizes to disengage the springs 116 and 117.

whereby the protecting potential is removedv from the connector bank contacts of the calling line, and thus when a subscriber calls his own line the connector switch will not receive the lnisyreleasev The rstselecter switch l) is a modified form oi' the seleetor switch disclosed in United States Patent No. 815,321, granted s pass over the A licliarel'i A3, 190i?, to Keith, Erickson & Erickson, with the exception that there are no normal conductors such as those of the Said patent. There is also no use in the selector switch D for a bridge-cut-otf relay, and it is also omitted. and the line relays are connected directly to the battery lead. The private normal conductor, such as the private normal eouduetor ol the said selector patent, is o1 no necessity in connection with the selector switch l), and is also'omitted. Since like parts are likewise represented throughout the drawings, the vertical magnet 96 and the rotary magnet 97, the release magnet 08. and the private magnet 99 will he recognized and understood. The said private magnet 99, of course, controls the side switch wipers 100, 101, 102 and 103,

the said priuite muguet also controlling the circuit elf the vertical magnet 9G, in the usual umnner, by means oi' the springs 105 and 10G. The vertical movement of the switch shaft, and, therefore, of the wipers 119, 120 and 121., controlled by the vertical magnet. and the rotary movement by the rotary magnet 97, the rotary magnet circuit hr 'ig provided with the usual .interrupfer springs 107. The operative magnets of the switrli. et course, are controlled by the subscriber through the medium of the vertical and rotary line relays 108 and 109, as is well known. Said relays have under their control the usual springs 110, 111 and 112. By means of the back-release relay 115 the release of the switch l) is brought about after the side switch has passed to third position.

The euiuiwtoi switch E may also be of any suitable or approved type, for instance of the general type describeddn the United States latent No. 815.176, granted March 13, 1906. to Keith, Erickson Se Erickson. provided with certain improvements. The mechanieal details of the first-selector and connector, as is well known, are very much the same, altlmugh there is some material difference. in the circuits. The connector switch shaft not shown), like the first-Selector switeh shaft, Carries the line wipers 125 and 126 and the private wiper 127. The eeimeefu switch is also controlled by the valli smsrriber tln'ough the medium of the r @si inni rotary line relays 128 and li; he vertical line relay 128 directly controls` the "vertical the rotary magnet reo lll

`Well-known manner, for @ech di Wipers 135, 136, 137 and 138, .wie switch of the connector, like the side seiten of the first-selector, has a normal or tiret position, a. second position and third posi tion. trolled by the line relays 128 and 1v jointly'. By the condensers 140 and circuit through the connector is di@f two sections. The centralvoifice is ein with busy-signaling apparatus orf my able design, comprising an interrupter in series With the primary Winding` or" the in diiction-ooil (for example, shown K), whereby a. busy-signaling current is inC in the secondary winding olf the A\ clearer understnmlingF of system may be obtained by i operation when one subscriber enit Assume, for example, that the sul) substation A desires to ei the e substation A to which is olotn, her 220. Then the receiver 2 from `the switch-hook 3 the sn uscends, carrying the rod 4.3 ont of 4 ment with the looking reiey if. 'i eeh the number 220 the subscriber at substation A operates the calling device ons n inra-the "l'ie preliminary impulse for operating switch C occurs when the selling rotates the dial forward for the whereby the rotary impulse pressed against ther ground post result, the trip magnet L7 of the hr (l is energized by :i fiori if entre ground G to the .sprr lo locking relay, to the s Y ground post '20, irnlmlsey spr rotary line Qonrluctor (Fig. out-off rel:

to the trip magnet si, trip magnet to the eo 157 and* S8 of the relay sprin S6 of the motor magnet Til, winding of the motor magnet tery lend 160, thence throi i, ground (l. Although th'1 theV motor ningiiet Tl. the not operatively energize, en@ net alone operates, As soon n; net LVI energizes. the armatore Si; is 1:" und the plunger JA is ilwr ted into thel honk terminal Q lfhen the plunger 44 en? ininnl Q` un energizing' eireiit through the motor magnet re1b y in turn operates to close oirfg; the` motor magnet T1. The moi`v then operates to place ih iide which :ire in loekingf engoge shutt opposite the next nel similar to the terminal. Q, 'We '"irenit through the relfiy T3 extends tr' 1 grwind G2 through the WindingA 151 oi? tif relay '73 to the segment 74, wiper erm 75, segment vilv.

1 h toe termi- The release magnet 1341 :il con- 34;, conductor 162, bank terminal springs 68 and o7, release magnet 4S to the battery lend 16|), thence through battery B to ground G. Although this circuit includes the release griet the said magnet does not operatively energize, since the, windings ot' the relay T3 :ire wound to n high resistance, while the winding of the release magnet is comparatively low. The `relay 73, upon en erlejizing, operates to place the springs 87 :md :8S in Contact, whereby n, circuit is completed through the motor magnet 7l, ex tending; *from ground G through the springs BT and motor magnet springs S5 and 86, thro h the Winding of kthe motor magnet to tl'e hnttery lend 160, thence, through hetteifv l to proximal G. The. motor magi" 't Yi upon energizing, attracts its armature 81, whereby the pnwl engages the ratchet ,fiee: 'f and rotates the said wheel one step. When the armature 81 attracted against .the mog'nrt cores the springs 85 and 36 dis* engage, thereby breaking the energizing oirooit through the motor magnet. The oumnrm 7G, being .in engagement with th pin T7A operated to ndreuoe the plunger shaft (2O nd eonsequontly all idle. plungers that may .Je in normal position) one step to nnother trunk terminal similar to the terminal (.2. l o7 the wiper T55 is ezirried from tl e conto-.t point 84, wliieh eorresponiis to the terminal. Q, to the oontsxct point 854. which letter corresponds to the terminal before which the advanced idle plungers are now resting. At the instant that the said plunger 214 enters the han" terminal Q, the oiiowing springs n e gres e. into Contact: 63 ond 64, 65 and G6, 61' land GS, and (S9 and, 70. 'lhe engagement ot the springs (19 and establishes a oironit from ground Gi, hy 'Way of the normal (conductor 95, to the connector private henk contacts correspondd ing to they line that terminates in the lino switch C, whereby a guarxfiing potentiel is set up to prevent any subscriber from calling: the said line after the calling subscriber at substation A operates his dial prepara tory to making a Call. :is expiained. `The circuit over which the said guarding' poten tial is established extends from ground G4, springs 116 and 117, through the bank springs 70 and 69 to the private normal conductor 95, thence to the connector private henkel, The engagement of the springs 69 ond T) also closes a circuit through the outofl relay 46, extending tron'i";grouiid G, springs 116 and .117, through the honk springs 70 and 59, conductor 16?. 46 to the battery lend 160. thene through battery l to ground G. The said relay, upon energizing. breaks the Contact "between the spring` 155 and 1:34. 1When the said springs disengnge, thel rotary line conductor 32 is disconnected from the trip magnet 47.

The closure of connection Abetween the i closing an springs 67 and 68 establishes a guarding potential at the master switch bank contact 84, over the following tiicuii from battery B to the battery lead 160,'thenee through the release magnet 48 andvsprings`67 and 68 over the conductor 162 to the said vcontact point A`84. It will be 'understood that the bank terminal Q, being the first bank terminal of the line switch bank, corresponds to the first segment 84 of the master switch bank O. his guarding potential protects the seized trunk conductors 90, 91 and 92 from bein seized by other plungers. Suppose that the master switch has operated and carried the when the motor magnet 71 operates for the next step, the wiper 75 engages the contact point 84 upon which there is a guardin po` tential. An energizing circuit-is established through contact 84 through t 1e wiper 7 5 to the common segment 74, and through the Winding to i ma et 71 from ground Gr3 sai springs 87 and 88, through the motor 'li magnet springs 85 and 86, niotorniagnet 71, thence to the batter lead 160, and through battery B to groundy The .motor magnet then operates, as previously explained, to rotate the ratchet Wheel 72 one step for advancing the plunger shaft one step, and the master switch bank wiper 75 is also advanced one step and brought into engagesecond segment 89., The

us advanced one step,

i in lookin previously explained. 'If there should be a guarding potential at the bank segment 89 of t relay and motor magnet 7l is again operated, the plunger shaft 60 and the inaster switch Wiper 75 are advanced another step. This the motor magnet e next subscriber makes a call. osure of connection between the 63 and 64 extends the calling sub- The cl springs scribers vertical line conductor 31 to the vertical t conductor 90 and to the sido switch Wiper 100 of the first-selector D (Fig. 1). The closure of Contact between 66 in a siinilar manner extion With the selector D and is ready to begin operatinv his calling device for the first digit. The rst digit being 2 the subscriber lector D, .lay 108 to tl presses the liuc relay spring of'said level.

operates his dial accordingly, grounding the verticahline conductor 31 each time that the spring is pressed'onto th rent from the substation the locking relay springs 40 and 41 ating 'ground springs' 18 and 19 ground post'20, f spring 23 to Athe vertical line conductor 31, line switch bank springs 63 and 64, vertical trunk conductor 90, side switch wiper 100 of the secontact oint 170, vertical line reie attery l through battery B to gr coperto the.

line contherefore, the e selector D. The from ground G and 66, rotar' trunk conductor 91, switch Wiper 101 of i point 171, .rotary line relay. 109, to the bat` tery lead 160, ground G. The relay 1 f the trunk conductor 91,

with the rotai'yl'ine relay 109.

The rotary line relay, upon operating, 112 onto the ground spring 110, thereby establishiriur a circuit through the private magnet 99 filoni d through the said magnet to battery lead 160, thence B to ground G. The pri- Vtween the side :f

rate magnet. upon 'energizing and denergizing, permits` the c`'elector side switch to pass troni first to second position, per1nitting the side switch wipers 102 and 103 to engage .the contact points 172 and 173, respectifelj-.Z vthe closure of connection heitch wiper 1021 and the contact point li'l s up an' energizing circuit for the rotary magnet 9T from ground GG to the contact point 1.73. through the .side switch wiper 103. interrupter springs 10T, rotary magnet JT to the battery lead 100, and then through battery l to ground (lr. The said rotary magnet 9T then operates to rotate the wipers 119, 120 and 121 o1 the selector l) into engagement with a trunk line leading ro some idle connector switch. and in the particular case under consideration to the connector switch It the wipers have to pass over busy trunk lines, then as soon asthe private wiper 121 engages a grounded contact point the private magnet 99 energizes again, locking the side. fsu-itch in second positipn. The energizin`-` circuit kliar said private magnet extends troni the grounded terminal G of battery B through an occupying switch (not shown) to the private wiper 121. thence oyer the, eonduetru 174, through the baelvrelease relay 115 to the side switch wiper 102, contact point 172, private magnet 99, thence through said magnet to the battery lead 1GO, and through battery B to ground (l. The private magnet 99, upon thusr becoming energized. lo'ell's the grounded side switch wiper 103 in engagement with the contact point 173, whereby the rotary magnet 97 will be energized intermittently until the wipers are carried beyond the lastbusy trunk line. At the instant that the. private wiper leaves the last busy contact point the energizing circuit through the private magnet 99 is destroyed` and as a result the selector side switch passes to' third position. 1t', iunvwer, there are no busy trunk lines, the rotary magnet 9T releases the side switch to third position as soon as the wipers are carried into engagement with the lirst trunk line. As soon as the side switch passes to third position, as stated, the subscribers line conductors 31 and 32 are extended to the conductors 175 and 176, which, in this case, it is assumed lead to the connector switch E. The extension of the line occurs, of course, as soon as the side switch wipers 100 and 101 engage the contact points 177 and 178, respectively. Not only is the subscribers line thus extended, but a guarding potential is established at the private wiper 121, when the side switch wiper 102 passes onto the ground Contact pointy 179, for protecting the seized trunk line troni inter ference by other calling subscribers. This guarding potential is established from ground. G9 to the Contact point 197, thence once. As a result the vertical line relay 128 ot' the connector E is energized twice and the rotary line relay 129 once. For the second digit 2 the vertical impulse spring 2?- is pressed onto the ground post 20 twice, whereby au energizing circuiit is closed through the vertical line relay 12S. This circuit extends from ground G through the ground post 20, spring 225. line conductor 31, springs 63 and 6l, trunk conductors 90 kand 1T5 vertical line relay 12S to the battery lead 100, thence through battery B to ground G. .Each time the vertical line relay 128 is energized, the line relay springs 19T and 19S are pressed into Contact, thereby closing an energizing circuit through the vertical magnet 130 which operates in the usual manner. one step at a time. The shaft wipers 125, 1:20 and 127 are, therefore, raised two steps and brought opposite the level in which are located the normal terminals of the line of substation #220. The rotary impulse spring 24 makes contact with the ground post 20, thereby closing an energizing circuit through the rotary line relay 129 extending from ground (1 through the ground post 20 and spring 21, line conductor 32, trunk conductors 91 and 176, ringer springs 200 and 199, through the rotary line relay 129 to the battery lead 160, thence through battery B to ground (l. The rotary line relay, upon operation, closes an energizing circuit through the private magnet- 133 which operates to release the connector side switch from first to second position. The last digit being naught the calling device is operated as previously described, grounding the vertical line conduc tor 31 ten times and the rotary line conductor 32 once. The vertical and rotary line relays 128 and 129 are operated over previously traced circuits. However, when the line relay springs 197 and 19S engage, a circuit is then closed through the rotary magnet 131 instead of through the vertical magnet 130. Each time that the rotary magnet is energized it operates to rotate the shaft and shaft- Wipers 125, 126 and 127 one step at a time until the said wipers are carried into engagement with the normal conductors 93, 94 and 95, the former two of which lead to the line terminals of the calling subscriber. The energizing of the rotary line i spring relay 129, as previously stated, complet-s an energizing circuit through the private 'i h now operates to release the side switch from second to third pigisition, thus placing the side Switch Wipers 135, 13b, 137 and 138 iii contact with their respective Contact points 195, 196, 204- aiid 201.

It Will ybe understood, ci' course, that the usy-release does when a subscriber calls back on his own line, will be explained.

net 133 energizes, as heretofore explained. At the instant that the said passes to third position, the connector side switch wipers and 136, having engaged thecontact points 195 and 196, extend the nection with the normal conductors 93 and f l conductors 93 calling line, it will be evident that the calling subscriber has operated to connect the connector E with his be remembered that when the line switch C irst operated to close the bank springs 69 and 70 into contact, the guarding potential was established over the private normal conductor 95 to the connector private bank contacts corresponding to the line allotted to the line switch C. One of the said contacts is now engaged by the contliat the energizingcircuit for the connector comprises the rotar private norinal relay 114 in multiple, en

operates the private magnet 133. It dent, therefore, that at the instant thail he connector side switch passes to third posi tion there is no guarding potential at the connector private bank contacts to interfere with the establishment of the desired connection. v

The calling subscriber having completed the call then proceeds to signal the called substation ln order to sin el the called subscril'iei the calling siowriber presses the signaling button 37,

' into engagement invefrie grounded contact point 38. As a result the vertical line conductor 31 .receives a current impulse from the substation ground G to the och-out relay springs tu and 4l, ground springs 18 and 19 to the contact point 38, spring 35, thence 33 to the vertical line conductor 3l. Y(irounding said conductor connector vertical line relay 128 over circuits that have been pointed out. The operation of the said relay 128 causes the energization of the connector ringer relay 132 over the following circuit: lfroin ground G7 at the connector through the line relay springs 19T and 198, private springs 158 and 159, side switch Wiper 138, contact point 201, to the ringer relay 132. thence to the battery lead 160, and through battery E to ground G. The energization of said ringer relay 132 bridges the ringer generator across the normal conductors 93 and 94, whereby ringing current is projected over the lineconductors 31 and 32 to the substation for operating the ringer 202 at thev said substation. It be explainedfhat the connector E, like all the connectors of the two-hundred furnishes only the ringer 202 of the substation #220 vvill be n saine line may t`they will not respond to said generator. Similarly, e connectors of the thre`e-hundred group, which are employed when substations of this gmpmre called, may be arranged to draw their ringin current from a ringer enerator that urnishesjcurrent of such clar-Y acter that only ringers tuned to respond to t e current of this particular character will be operated. Lik

our andone lhundred groups may 1n turnk ot the ringing current 204, through y he vertical normal conductor 93, thence to .the vertical line conductor 3l, cani-arm switch-hook, and spring engage when the switchook is at substation #220, condenser 207, back to the rotary line conductor 32, thence over the rotary normal conductor 94, wiper 136, relay springs 208 and 209 to the ringer generator R. The subscriber at subthiough the springs 34 and.

It is evi-jv current is through the ringer 202 va0 y can station #220, upon responding7 hritlgffs hhs reeelrer 2]() in Series with the rundem 21h.

which is in series with the onderw-r i2y :xml semnrlziry windingV F32 of the heel; when rising permiu` the npring .211"

:Z13 nml 216 :nui the 5min 's 21T :uni :l te engage hefore thtl sprin'ls il mul 212() lisv engage.y in which ense the suhstzltion hiv/limit relay 221 t-nergizesy over me fullmximf rireuit: from the Suhstntien pjrwulnl (i. through the springs 221i :mtl 223, Y :ML springs :521' nml 2212 to the relmV zl, theme through the spring 215 and '.914'V 'te the witirzil mwhirter 3lf :nul Yertiml pri` rute nm'runl relziy 1153 nml wrtirn'l line remi" 128 nf the venneetor ll in multiple tu the buttery lezul 111i, theme through lilith-ry l tu ground (i. lThe uhfrtaxtien upm; euerfl ;il,1u"l-2:lml funn w i frzuuxw't loch-wml reim' ut' ful", miuu il-ihre: w: 'mii reilly LA vuerf' umm; parat llwtrrrring the #.mnfvtinn l-vtmi the ffututivin fwnnal U" nini hr nmuml wringj :ffl-. we that thv iffalrprivrll it the nieuw; tm' fruumliug wither ut' the line ontluvwr Ill nl 12.

lig. While sii ring ill result; ui w -im f-nvmn nu l lhu, hwhug thv reliijv 221 reflpwt 2f; ullmifu 'I' the sulwfwilzer :il :auhhtvulien tlju thmeturen :mnh- \\'er!e. to interfere with tuj' rstulllml emmertifnn :since hin` gjrfxunai is eut et?. :iq explained in eminm'ti-m `ith ullfstfiiwn #2245. Ut' emuwlwrilw :euhsei'iher xt "fri hurri-` up his retffirer is rrirriefl ihmr. h f thu viii'wh rela' ihr-NM1' Y. uulwl oiplnizml. 'l`lu wenn; t' :Riti: V:i thv :Mlist-tien W) nifl tht ,"lt'er the sulwi'rili-r :rrrJ thrafulth luim li! the Suifsrriiwr nl' Hiahstmien `iltr() hm up hi# reeeirer he 51111111135 the wrtieu :um retin-.r line ennfluvtera l1 uml 115 eiinultunw firmly. thereby prmlueing n release (lf the Switehes through the nietliuin of which the connection has been establisheel Ar; the switelrhuok 3 desreiirls. the relejage springs 1 8 und are pressed into Contact, '\\'herehy the vertical :xml rmnr \A line rnmlucters nre grounded. lfneler there f'fomlit: s

., im line relay@ 12S und 129 are encrgizeth whereby the trnnlvrelense springs 227 and 22h are prvsnwl into Contact. with the result that zu. em-J'L''fzinjg eirf'uit is established through the z we muguet 1254- ef the connecter E in ith tha? haeirrelmse relay 115 of the iw-Mr i) The release magnet 131 of -':m1rv-r umn energizing. restores the f`--u`fh und the Switch Shaft t0 nurninl l i thv weil known manner. :it whlffr tive the line uml private wipers 125, W13 :unl 12? are, of emu-se, disconnected 'l'runi the no1-nml rumluetms 93, J1 :mtl 95. 1h energifiug o1' the lizuzlereleuse relay 113 rr-rrif' the hm'k-rs'fleuse relay Springs 229 :i i w engagement, as :1 result enerfhnise magnet 9S frein ground the Suid springb` Q29 and 230, (1st magnet 98m buttery l5. The 1 magnet u8, upon energizing, nature :intl puta` the szuue in fe lewe the srviteh when, thc re- 4 :u the suheemtihn disent): ge, as ih@ hmlrrelense relay 115 19,11# the magnet 18, hut :also minet ILS if tho line switch C,

inl refimnlugrnel 15 is emmectecl wtuiith the release n'mgnet 9S of i), the furent lin-ugh the muguet 1:"k iluws 'from gmund thI hwk-release relzry Springs ,1 n the third trunk emnhrctor thr'vigh ihe line Switch bank l 1. through said magnet 48 will ital), und through barhen the reliable ningrggims. the :.irnmture 15) the Armature ,Si of the :unl the erljfh tererminni 3T #il the thus in r -aulnefs ,Y with when the dmnergizen sufl'ieientlSf'. 'tration release springs 7, ie energizing eireiutz-y Of the 1W; l i, wrifffii line relays 129 und 12S mi' the rminwtur ll are destroyed. As a remit. the hner fing; circuit thrnugh the v 'l irxgfnfft 'lluzul the lmeklrelense re- 15 if; hrnluyn restoring the eenneetur iflition. The dener- '-rieae relay 115 in turn mien of the Sehrter rei the rersrll already etated,

Eil? :ma

ihr (lenergimtinn of the hf nl' the line switch C. f v. mgljnet 48 0f the sind line ergizerg the plunger 4L through 'the metil i 01" the nrnmtures 51 and 19, f1S Mtliilrmvl; :mtl lifted into engagement with the plunger shaft GO. destroying, of enurse, the energizing circuit 0f the cut-oil' relay 46, removing: the guarding potential from the insister switch henk O. and from the connertnr hriniis, and disrnnnecting the 51th th(` Calling siihscrihrr. in whirrh Juso thtt oonueotor wipers 12.7, 12o und 12? will ihlibrh connu-tion with normal conductors other than the normal conductow 95h lll and D3,

whirh normal conductors will` of course, he nl otteil to the other line. In that ctisew that is, when the sul'iscriher at substation #420 is connected with a' sulmcril'er of soin@ other linen-thon if the s1iiis i'ili0r zit,- onlptp to rome in on thi-y lint` thiA Qiwrgizi circuit for tho mi tion iorrli-niit rch@ ron'iprises thc vertimf private normal relier 1.13 :uni thi: ronmctor wrtifffii lino wht 125,. :w explained. lt will ho miti mow. tlm Y tho pritnti fiorini:-

guarding potee'itiial t+1 hector privatif lfiiiilt with-:rt desired line.' ln that MSB, as is woll lwonxx, the cor/ncifttw sirio switch l f--1 iii-t, guns t1,- thid pmi( init i reir@ nl? 21ml thv r ing' suhat-t ihr-r rvctfiws 21 lump mul The iiiisiYit-,iivnw gwf'iiis when tinrx foto line.cozitlzufti'ir f is lfzoiiih'h'il 'for thil hot time., ,fi ail :11.` th",x *A "lef, privinr mitghzi, l? viivrliyzof-l. :it hint timo thu primtv Living.; i :imi 'lz :i i iwf. imo ent/fn nent :intl :in ooiigfizing rimini. e lii 'limi thi' Q'li lim :ifs ftllow; 'lim t, flows l'itlin vate hunk contfirt tu the prix; hf SithA switch wiper 13T, prix-:sw rings and 2317 release, n'iiigniet ll. rhtnou through buttery t0 ioiinfll. This l:i:-t rw* puls@ sonic. in while: thiJ hi second po. tion. il t'zcr the ronnwtor le soil than il th vulling mlm 'l h rnizfltf button T he granuli. thu vor irme ,w tim ver t, l i o trionfi ning:

or viii mit ifoziiiwtoz' .mil morti ibi-fnl linee 'wlzij, oi 'tho iioinitor. mi aiv misas lite connector :Mitth riuniti h'hifii hittor, upon rising. closes tho otr-normali springs 233 and 254, thereby4 tuhlisshing a busy-signal through the culling; Siihbtution. The busy-signaling current flows from the secondary winding of the busy coil 104 through the olf-normal springs F281 and 2253 to the side switch wiper 13G, thence through the Condusor 141 to the calling substation, and hack over the vertical side of the. lino through the vertical line relay 12S and private normal rainy 113 to the battery lead 160, and back to the coil 1011.. When the `atingrk calling iihstfrihor haar@ tliolmsy-Signal he hangs; up his 11i-wiwi' :mil grounds both ot' the` lint conductors ill und 32 Silnliltnno ouali'. thereby envi-@Zing tho vertical :intl rotin-V lint rvl:iy.-; unil 121). with the re- `mit, already c\'pi:iinc i--thnt is, with the result thi: allot thil switohis are relousotl :intl ruhtorrtl to normal ronilition. Suppose that thv :'fziiiistathh is f'ulltil hy :inotho :stilista om #CMU for vxzisnplc. A Sumo that thv liiiiyhwitffh allot/lofi to tht liml #500 Heizos thv trunk line loading' to tho hist-sw lector l). :mel assumo, also. that the connrrtor lil i5 ot' the tour lninih-vil group and is thu om sielevtvil h3' thi' tirstmrlector l). lh@ oielziiill 'ml coniir-liosi mi hl then he thiV` amine :its that fhown in l"if l, except that the trmlf liml lvmiing; to thiu vonnvt-tor li wmihl he rouwt-loi with Ehi lim: fwitch .failotti-il tt thi`A iii Emi iiisiimial oi' with tho :is .xliown ln that (also, if a il on tiro suini? iinr ai tho i.; locatari wore to rvmoo to mula@ :i will opirzitioia 1:5 thif i without limiti iii wp" .num 'hviiohf: has :':iiwl lim; this rc' if: somo zo; thv rrlmist" diri-:niv iloinvalq :mtl itimiwotion with tho nihil line i5 :eti-vwd n1 :soon :is: thv comit-rtw Wipers "mi from #hai lmaiits.

lffrftoiiij; it wil lio'smh tlmt i'iifws-Js without, lieiliilitv y'ingr thiL trip i; nrt l?, :is tht` @nw of thiy ruim' i zitter flows :x ,'siihstitiiti vili-veilt tim hihihi in thiswhy. im* voimwior tutti rfslvix miti iinx mehr :mi rwrgjxv. :tml till the ut-otl' rvivy ll? will tlhf i. lrgizix litt-ruim there is Qtiil n otrzil ground cin-nit throngh'tllo winding: of rh tht-ntl' rilrv. With this nrrnligi-inont ihr writ-whos will rilimzw with rertziinty, und ihility of 'fing the individuali ingr switrh oi'isrn'mi is preriutletl or fw fir refhicetl lt will he sewn, ot' colarse, thfit the? ri :fr 11S (loco not iutrrcrf: withithe monti-,nlug interruption of th` guarding potontiiil h5' the relay 114, when :t suh- Scrihigr on i party-lino calls]k hack on the Home hrw for tho purpose of ronnnunicating with another Subscriber thereon.

It will he ohvioiis that in this system the resistance of thvl nmgnots may be varied to :my extent consistent with the successful operation of the saline. 1Sotonly muy the rosistzxnccs of tho linir` relays (for example the ,line relays 12S and 12M of the Connector E) he varied. hut the rvshtanfso of the operinagnets (for example the role/ase la .fi

magnets 48, 98'and 134) may likewise. be varied. It will also be obvious that the springs used as contacts may be adjust-ed in -any manner desired and their tensions CIK varied to any extent in order to control the speed andV operation of the `armatures asso elated with them. For example, the sprin f of the motor magnet relay 73 may be stiliened or weakened, as may be found Couven ient or desirable. In regard to this motor magnet relay it should be stated, and it perfectly obvious, that although it is shown as a double-wound differential ,coil the upper winding is not absolutely necessary, since the system will operate without it.

lVhat I claim as my invention iszl. ,In a telephone system, a Connector, a. line, a plurality of subscribers' suhstations thereon, a. trunking switch, a cut-off relay therefor, .means for estalilishing,r a guarding potential when the line is in use, means for momentarily removing,r said guarding potential when one of the subscribers calls hacken the same line. a circuit for ener gizing said relay duringy conversation, means for releasing the eonneeti'ir, and arother circuit for enereizing said relay alter l opened to presaid irst-nzentioned circuit. rent operation of said trunlting; su. roh dur ing the release.

2. vln a telegihone system. a connector, a line, a plurality of subscribe substations thereon, a relay individual lo... ifl line, means for establishing a guarding potential when the line is busy, automatic means for nu;- mentarily removing said guardingy potential when one of the subs( jibers calls harh on the saine line, means for hee@ said relay energized during eonyersation. mean.' Vl'or releasing the eonneetor, and autonuztio means for closing a local circuit through said relay when a. subscriber lungs up his reeeiver to prevent deiinerggizatiui ot' said relay during,r the release.

3. ln a telephone' system, a line` trunk lines., an individual trunking switch l'or said line. and a pair olA relays hrfilged :i-,wross nach trunk line. said trunkingl switch provided with a out-oil' relay, and energizing circuits for said eut-olll relay, the relays of the trunk lines being provided with means whereby the energizing of any pair ot' relays serves to open one eireuit and close. another through the said eut-olf relay.

4. In a telephone system` a line, a relay individual thereto, a callin;r mechanism, switches controlled thereby, means for keep-- ing saidrelay energized during use of the line for conversational purposes, a plurality of energizing circuits for said relay, and means for opening one circuit and closing another when a subscriber on said line hangs up his receiver.

5. In a telephone system, a. line, a relay individual thereto, means for energizing said relay during use of the line for conversational purposes, a trunk line, a pair of relays bridged across said trunk line, and means whereby the energizing of said pair of relays opens one circuit and closes another through said rst-mentioned relay.

G. in a telephone system, a line, a plurality of subscribers substations thereon, automatiey means for establishin` a guarding potential when the line is busy, auto- 75 :natie means for momentarily reuioying said guarding potential when one of the subscribers calls back on the same. line, al relay individual to the line, means for energizinfg the relay. and automatic means Vl'or Se preventing the deenergizinfb'A of said relay during the release.

ln a telephone system, a line, a trunliselecting switch Connected thereto, a out-oil' relay in said switeh, two circuits therefor, S a talking circuit` controlled by said relay, a pair of relays connected in multiple, and means whereby the eilerfriziner el" said pair of relai-:s opens one eirruit and @loses au other through the said rut-oli relay 9o S. in a telephone system, a trolling' magnet normally vonnis with, a 'mt-oli relay ior diseona itroli. 2;* magnet 'lroni the li rrr io ul ent-ol.' relay, a t; ig enfuit 35i monti-oill said eut-oli' relay. a pai:A et relays ronneried in multiple, and means whereby the energizing oi' said pair of relays opins one rirruit and rloses another through the said rut-oil relay.

fl. 'n :i telephi'nuj system. a line. a trut-lli.i` ing' swilrh lor said line, a rutolli relay tY t for, two circuits for said relay` r'ireuit uontrolled by said relay, a relays. and inea-iis whereby i oi'L :aid pair of rela ifloses another throl the f. irrf il). ln a telephone system,

trolling` magnet normally minneettal tllei with` a rut-oil relay for diseonneetin said controlling magnet Vlrom the line, two ou'` suits for sail. eutoll' relay. a talking; Circuit controlled hy said eut-oli relay, a. pair ot relays. and means whoreb the. energizing of said pair of relays opens one ,circuit and closes another through the said rnt-olf relay.

ll.. in a telephone system in which the subscribers lines are divided into groups, means having one motion to select groups and another motion to connect with a line in the selected group, line, a plurality of subscribers substations thereon, ar trunking switch. a cut-oli relay therefor, means for establishing a guarding potential when the line is in use, means for momentarily removingr said guarding potential when one of the subscribers calls back on the same line, a cirruit for energizing said relay during conf vt'or said cut-oll relay. the relays said relay after said rst-mentioned circuit is opened to prevent operation of said trunking switch duringr the release between call ing and called subscribers;

12. In a telephone system in which the subscribers lines are divided into groups, means having one motion to select groups and another motion to connect with a line in the selected group, a line.y a plurality of subscribers suhstations thereon.l a relay individual to said line, means for establishing aguariling potential when the line is busyg automatic means for momentarily remo ing said guarding potential when one. of the subscribers calls hack on the same line, means for ykeeping said relay energized during conversation, andt automatic means for closing a local circuit through said relay when a subscriber hangs up his receiver to prevent denergization of said relay dui`A ig the release between calling and called sahseribers.

i3. ln a telephone system in which the. subscrihers lines are ldivided into groups, means havingone motion to select groups and another motion to connect with a line in the selected group. a line. truuk lines, an individual trunlting` switch for said line, and a pair oi' relays bridged across each trunk line` said trunlting switch provided with a cut--oll relay, and energizing circuits of the trunl lines beingr provided with means whereby the energizing ot any pair of relays serves to open one circuit and close another through the said cut-oil relay, v

i4, ln a telephone system in which the subscribers"lines are divided into groups, means having one motion to select groups and another motion to connect, with a line in thel selected group. a line.I a relay indi vidual thereto` means for keeping said relay energized during' use of the line for conversational purposes, a plurality ot energizing;r circuits for saldar-day, and means for opening one circuitwnad closing another when a suhscriberon said line hangs up his receiver.

15. In a telephone system in which the. subscribers lines are divided into groups, means having one motion to select groups and :mother motion to connect with a line in thc selected group, a line, a relay individual thereto, means for energizing said relay during use' of the line` for Conversational purposesI` a trunk line, a pair of re lays bridged across said trunk line. and means whereby the energizing o'f said pair of relays opens one circuit and closes another through Said irstanentioned relay.

16. In a telephonesystem in which the subscribers lines are divided into groups, meansl having one motion to select groups and another motion to connect with a line in the selected group. a line. a pluralitv of snl'yscrihers" siila-tatioiis thereon, automatic means for estahlishing' a guarding' potential when the line is busy` automatic means for momentarily removing said guarding po- "ential when one of the suhscrihers calls back on the saine iine.y a relay individual to the line, means for energizing the relay. and automatic means for preventiugry the dein ergizing ot u relayY dui 1 3 the releasel 17. In a ephone system in which the subscribers lines anx divided into groups, means having),` one motion to select groups and another motion to connect with a line in the selected group, a line, a tiiiiik-select 'ing switch individual to said line,y a Cutoff relay for said switch, two circuitsy for s; "il relay.y a talking circuit controlled hy saicl relay. a pair of relays connected in multiple, and inc ns whereby the I i j said pair of re'fvs one closes another through fh 1S. ln a telephone system in u suoscriners lines are :ha means having one Y and. another motion io in thc selected group magnetnorinally coni oili relay for disconn therewith, n i; i h I :d conti illin magnet from the liner two circuits 1i cut-oll relay. a talkingF circuit controlled hy 95 said moet? relay, a pair ot relays connect` ed in multiple. and incarna w" crgizing of said pair of' Z circuit. and closes another thiwug'i t cut-oil' relay.

iii ln 'a eleplzoin suhscribers lines are means lnivinf` one i and another i non to in the selected group. i magnet normallyconne f ofi' relay for diseonmagnet from the line. eut-off relay, a talkinghy saidwut-oll' relay, a A means whereby the energizing o of relays opens one cirenit and other through the said cutoff rcl 20. n a telephone system, a subscribe s individual line switch adanterl to perform ng op- :i l relays, anni l' .said pair closes an a preliminary non-Iuuncrical truni eration, a private normal conductor, i i means normally disconnected from said switch for maintaining a ground on said conductor until ythe switch is released.

Signed hy ine, at Chicago. Cook county. Illinois, this 26 day ot' June.y 190i.

ED'YARD A, MELLINGER Witnesses z Enwann D. FALns, ARTHUR B. Ernani'. 

